Liver Regeneration: Influence of Interval Postextirpation on in Vitro Growth of Cells from the Remnant Liver 1

During the first 48 hrs following subtotal hepatic resection in the rat, the principal indices of replication of cells in the remnant liver reach a peak and decline. These include: (a) RNA precursor uptake (1-2); (b) tissue protein synthesis (3); (c) DNA precursor uptake, in all types of liver cells (4); and (d) mitotic indices (5). The present study suggests that the increased in vitro growth potential of remnant (regenerating) liver cells is found only in tissue removed more than 48 hr following the hepatic extirpation.

Method. Excision of the right portion of the median and left hepatic lobes (approx 55% hepatic resection) was performed in 90 male Long Evans rats (complete diet); and excision of the right portion of median lobe (approx 25% hepatic resection) in 90 similar rats. Liver tissue was removed from the caudate lobe (not contiguous with either prior resection) of 12 of these rats (6 with prior 55% resection, and 6 with prior 25% resection) at intervals from 6 hr to 7 days following the original procedure.

The regenerating (caudate lobe) liver tissue from each group of 6 rats (30 groups) was pooled, minced, and trypsin-dispersed. Cells were counted and cultivated (1.8 × 10⁶ cells/plate in 10 plates/group) in Eagles'medium supplemented with 10% calf serum at 37° in an incubator constantly flushed with 5% CO₂. Medium was replaced at 3 day intervals (4X). The attached cells were removed with trypsin and counted in a hemacytometer after 16 days cultivation. The values in Table I are the mean cell count in each group of 10 plates. Rats were weighed immediately prior to the first extirpation (Table I). Experiments were started between 9 and 10 a.m. in Dec.-Jan.(Los Angeles).